1. Technical Field
The present invention relates to the loading and unloading of flowable cargo transported in lined bulk cargo containers. In particular, it relates to a method and apparatus for rapidly constructing and installing liners in a container and rapidly attaching input, vent, and discharge ports to a container.
2. Background Art
Transportation of containers for bulk commodity products (grains, etc) have been implemented using a variety transport vehicles, such as trucks, railroads, and ships. Depending on the nature of the cargo, liners may have to be installed to protect the cargo from contamination (in the case of foods or other perishables) and/or prevent leakage (in the case of powders, small particles, etc.).
An important economic factor in the transportation of bulk commodities is the speed and ease with which the commodities are loaded and unloaded from the container. One factor which effects the speed, and consequently the cost, of loading and unloading containers used for the transport of bulk commodities is the time and expense of installing the liners.
The prior art has developed several methods of installing liners. One method is the use of mechanical clamping devices to hold sections of liner material together. This method provides flexibility in terms of sizing the liner for a particular load size, but it also has several drawbacks. In particular, the liner is labor intensive to install, which increases the ultimate cost of the cargo. Likewise, it requires additional components, in the form of the clamps, which increase the total cost of the liner. In addition, a clamps failure can result in substantial leakage of cargo. Cargo leakage can not only cause economic loss due to the cargo loss itself, but depending on the nature of the cargo, there can also be substantial environmental costs due to contamination and cleanup expense.
Another prior art approach which addresses the potential leakage problem has been the development of heat sealing methods (heat seals may also be referred to herein as welds) to fuse the liner sections together. Heat sealing provides an effective seal which eliminates some of the negative aspects of clamping systems. For example, the clamps are eliminated which results in lower cost for the completed liner. Since the liner can be completely sealed, improvements in leakage avoidance may also be obtained. However, heat sealing methods also have drawbacks similar to clamping methods as well as drawbacks unique to themselves.
While the cost of clamps are eliminated by heat sealing methods, those costs may be offset by the cost of the heating equipment used to create the seals. In addition, heat sealers have the same safety hazards common to all heating devices used to create heat seals (or heat welds). A third drawback to this type of liner construction is the labor required to create the seals. The more carefully the seals are created, the higher the labor cost. On the other hand, the faster the seals are created, the greater the risk of leakage.
In addition to the construction of the liner itself, there is also the issue of how cargo load, vent, and discharge ports are incorporated into the liner. Typical prior art approaches use heat welds to construct load, vent, and discharge tubes. Of course, the same drawbacks associated with heat sealing the liners apply to heat sealing these tubes. After the tubes are constructed, they must be attached to the liner. This procedure is also usually done via heat sealing. The wall of the liner encircled by the tubes can be opened at this time or when needed. If opened immediately, the discharge tube must be tied until unloading to avoid leakage, and the load and vent tubes should be tied after loading to avoid contamination.
An alternative method of constructing the tube is to used preformed rigid tubes or rings which attach to the wall of the liner. An advantage of this approach is that it eliminates the time required to construct the tube. The disadvantage is that the preformed tubes must be attached to the liner, typically by heating.
While addressing various aspects of constructing liners and their associated load, vent, and discharge ports, the prior art has typically provided methods such as the clamping and heat sealing methods discussed above. While these methods provide effective liners, they have numerous drawbacks such as high material or equipment cost, high labor cost, safety concerns, and the possibility of leakage, environmental damage, and cargo contamination. The prior art has not provided a method of constructing liners which can be rapidly and easily installed, provides a continuous seal, and requires no special equipment. The prior art has also not provided a method of rapidly installing load, vent, and discharge tubes without special equipment or extra material. Further, the prior art has failed to provide methods of rapidly attaching materials which are incompatible or are not heat or RF sealable.